原生JS如何监听移动设备屏幕横竖屏的旋转

window.orientation 对象在手机上才可生效。

<script type="text/javascript">
    var evt = "onorientationchange" in window ? "orientationchange" : "resize";
    window.addEventListener(evt,resize,false);
        function resize(fals) {
            if(window.orientation == 0 || window.orientation == 180) {
                    alert("竖屏");
                }else {
                    alert("横屏");
            }
        }
    resize(true);
</script>